1. Field
The present disclosure relates generally to systems and methods for displaying information for indicating the state of an aircraft to a flight crew. More particularly, the present disclosure relates to displaying information indicating the energy state of an aircraft to a flight crew as the aircraft is descending to land.
2. Background
Airspeed is the speed of an aircraft in flight relative to the air around the aircraft. If the airspeed of an aircraft is too low, the aircraft may stall. An airspeed that is too high during cruise flight of the aircraft may cause flutter. An airspeed that is too high during an approach to landing may cause damage to the aircraft flaps or other aircraft systems.
Ground speed is the speed of an aircraft with respect to the ground over which it is flying. At certain times during the operation of an aircraft, it may be desirable that the ground speed of the aircraft is not too high or too low. For example, the ability of an aircraft to fly through wind shear conditions may be reduced if the ground speed of the aircraft is too low during an approach and landing operation. If the ground speed of an aircraft is too high during approach and landing, the aircraft may land beyond the end of the runway, or may land at a position on the runway and with such speed that it may be difficult to stop the aircraft before the aircraft reaches the end of the runway. The desired upper limit of the ground speed of an aircraft during an approach may be determined using a stopping distance calculation for the aircraft.
A pilot or other operator of an aircraft may control the speed of the aircraft, both the airspeed and ground speed, by controlling the pitch, power setting, or both the pitch and power setting of the aircraft. Changing the pitch of the aircraft changes the angle of attack between the aircraft and the oncoming flow of air through which the aircraft is flying. The power setting of the aircraft may be changed by changing the power delivered by the aircraft engines to move the aircraft through the air. This power is often referred to as the thrust provided by the aircraft engines.
A pilot or other operator of an aircraft controls the aircraft so that the airspeed is within desired limits. Currently, ground speed is not usually considered during many aircraft operations. However, considering ground speed may be helpful in some aircraft operations. For example, considering the aircraft ground speed may be helpful in performing approach operations in gusty wind conditions.
Controlling an aircraft so that both the airspeed and ground speed of the aircraft are within desired limits may be challenging in some cases under some operational conditions. For example, a sudden increase in the headwind encountered by an aircraft during an approach and landing operation may cause the airspeed of the aircraft to increase suddenly. A human pilot, or automatic control system, may respond to the increase in airspeed by reducing the power setting of the aircraft. However, reducing the power output of the aircraft engines may reduce the ground speed of the aircraft to a speed that is below the desired ground speed for landing the aircraft. For example, reducing the power setting in this case may reduce the ground speed below a desired ground speed for responding to wind shears, downbursts, and other sudden changes in the winds around the aircraft, such as when a headwind gust suddenly dies out.
Accordingly, it would be beneficial to have a method and apparatus that takes into account one or more of the issues discussed above as well as possibly other issues.